Degree Of Interpenetration Research Articles

The effect of chain interpenetration on an ordering process in the early stage of polymer crystal nucleation

In the present study, the degree of chain interpenetration was considered as a structural attribute of the entanglements in polymer chain system. Inter-chain radial distribution function (RDF) was used to perform this measurement. We applied this method to a model system, in which an ordering process in the early stage of polymer crystal nucleation at the atomistic level was simulated by means of molecular dynamics (MD). Initial chain structures possessed different degrees of interpenetration and underwent the ordering process at 400K. Obtained results indicated that at the nanosecond scale the degree of interpenetration impedes the ordering process remarkably, which agrees with the experimental observation at laboratory time scale. Such behavior among chains indicates that at the atomistic level a creeping polymer chain is able to recognize if the neighbor group on the ‘tube’ is from the same chain or other chains. This recognition manifests that the reptation time of a chain would be influenced by the ‘tube’ composition or the degree of interpenetration. It also showed that the degree of interpenetration changes little during the ordering process, which means that the motion of the chain segments is mainly predominated by the ordering process rather than further adjusting the entanglement extent under the conditions simulated.

Synthesis and characterization of crosslinkable latex with interpenetrating network structure based on polystyrene and polyacrylate

AbstractFunctional poly[styrene‐co‐(2‐ethylhexyl acrylate)‐co‐(1,6‐hexanediol diacrylate)]/poly[(methyl methacrylate)‐co‐(butyl acrylate)‐co‐(methacrylic acid)‐co‐(diacetone acrylamide)] (PS/PA) semi‐interpenetrating polymer networks (semi‐LIPNs) containing ketone carboxyl groups were synthesized by two‐stage emulsion polymerization, and characterized by Fourier transform infrared, transmission electron microscopy, dynamic light scattering and DSC. A unique feature of the PS/PA semi‐LIPNs is their ability to crosslink and form thermosetting full‐IPN polymers through the reaction of ketone carboxyl and hydrazide in the course of film formation at ambient temperatures. Series of latex particles with various levels of crosslinking density in the PS and PA domain and varied composition of PS/PA LIPNs were obtained. The effects of the LIPN PS/PA composition and the level of crosslinking density in the PS and PA domain on film density, swell ratio, mechanical properties and contact angle with water were investigated. Maximum synergy effects obtained at around 50/50 (PS/PA) in terms of mechanical properties, density and contact angle with water indicate that the maximum degree of interpenetration is obtained at this composition. Copyright © 2006 Society of Chemical Industry

Statistics of Knots, Geometry of Conformations, and Evolution of Proteins

Like shoelaces, the backbones of proteins may get entangled and form knots. However, only a few knots in native proteins have been identified so far. To more quantitatively assess the rarity of knots in proteins, we make an explicit comparison between the knotting probabilities in native proteins and in random compact loops. We identify knots in proteins statistically, applying the mathematics of knot invariants to the loops obtained by complementing the protein backbone with an ensemble of random closures, and assigning a certain knot type to a given protein if and only if this knot dominates the closure statistics (which tells us that the knot is determined by the protein and not by a particular method of closure). We also examine the local fractal or geometrical properties of proteins via computational measurements of the end-to-end distance and the degree of interpenetration of its subchains. Although we did identify some rather complex knots, we show that native conformations of proteins have statistically fewer knots than random compact loops, and that the local geometrical properties, such as the crumpled character of the conformations at a certain range of scales, are consistent with the rarity of knots. From these, we may conclude that the known “protein universe” (set of native conformations) avoids knots. However, the precise reason for this is unknown—for instance, if knots were removed by evolution due to their unfavorable effect on protein folding or function or due to some other unidentified property of protein evolution.

Polyisobutene/polystyrene interpenetrating polymer networks: Effects of network formation order and composition on the IPN architecture

In order to improve polyisobutene (PIB) mechanical properties, a PIB network is combined with a polystyrene (PS) one into an interpenetrating polymer network (IPN) architecture. PIB network is formed by alcohol addition between the hydroxyl end groups of a telechelic dihydroxy-polyisobutene and a pluri-isocyanate. PS network is synthesized by free-radical copolymerization of styrene with divinylbenzene. Thus, the optimal synthesis conditions are determined by FTIR spectroscopy and the kinetics of the alcohol–isocyanate addition is studied in detail. A short kinetic study of the PS network formation inside the PIB network is also carried out. The highest degree of interpenetration is obtained by forming the PIB network first. The corresponding transparent IPNs exhibit two mechanical relaxations corresponding to those of PS and PIB enriched phases. However, mechanical properties of PIB networks are tremendously improved by the presence of a PS network in such IPN architectures.

Theory of glassy dynamics in conformationally anisotropic polymer systems

A mode coupling theory for the ideal glass transition temperature, or crossover temperature to highly activated dynamics in the deeply supercooled regime, T(c), has been developed for anisotropic polymer liquids. A generalization of a simplified mode coupling approach at the coarse-grained segment level is employed which utilizes structural and thermodynamic information from the anisotropic polymer reference interaction site model theory. Conformational alignment or/and coil deformation modifies equilibrium properties and constraining interchain forces thereby inducing anisotropic segmental dynamics. For liquid-crystalline polymers a small suppression of T(c) with increasing nematic or discotic orientational order is predicted. The underlying mechanism is reduction of the degree of coil interpenetration and intermolecular repulsive contacts due to segmental alignment. For rubber networks chain deformation results in an enhanced bulk modulus and a modest elevation of T(c) is predicted. The theory can also be qualitatively applied to systems that undergo nonuniversal local deformation and alignment, such as polymer thin films and grafted brush layers, and large elevations or depressions of T(c) are possible. Extension to treat directionally dependent collective barrier formation and activated hopping is possible.

An algorithm to simulate packing structure in cylindrical containers

The aim of this work is to propose an algorithm to simulate the packed bed structure of mono-sized spheres in cylindrical containers. The approach employed is called soft spheres algorithm, because it allows some degree of interpenetration between particles. The force balance accounts for gravity and contact force (to take into account the interpenetration), and neglects the friction force between particles. The algorithm provides detailed information about packing structure so it can be employed to evaluate local and global properties. The results fit better the experimental information than previous algorithms from the literature.

Polyisobutene–poly(methylmethacrylate) interpenetrating polymer networks: synthesis and characterization

Interpenetrating polymer networks (IPNs) combining polyisobutene (PIB) and poly(methyl methacrylate) (PMMA) networks were prepared using a in situ strategy. PIB networks were formed by isocyanate—alcohol addition between the hydroxyl end groups of telechelic dihydroxy-polyisobutene and an isocyanate cross-linker, catalyzed by dibutyltindilaurate (DBTDL). PMMA networks were obtained from free-radical co-polymerization of methyl methacrylate (MMA) with ethylene glycol bismethacrylate (EGDM) in the presence of dicyclohexyl peroxydicarbonate (DCPD) as the initiator. The synthesis of each network during the IPN formation was followed by FTIR spectroscopy. The highest degree of interpenetration is obtained by forming the PIB network first. The corresponding transparent IPNs exhibit two mechanical relaxation temperatures as determined by Dynamic mechanical thermal analysis (DMTA), corresponding to those of PMMA and PIB enriched phases. Mechanical properties of PIB networks are tremendously improved by the presence of PMMA network in such IPN architecture.

An unprecedented fivefold interpenetrated lvt network containing the exceptional racemic motifs originated from nine interwoven helices

An unprecedented fivefold interpenetrated lvt network, containing the rare racemic motifs originated from nine interwoven helices, is reported, which represents the highest degree of interpenetration presently known for 3D nets containing only planar four-coordinate nodes.

Morphology, microstructure, and mechanical properties of a copper electrodeposit

This paper presents two new experimental observations on electrodeposited copper: unusual morphology as seen in the scanning electron microscope at high magnification, and mechanical properties, as measured by tensile testing. We report detailed characterization of a 2.6 μm thick copper electrodeposit, made on silicon using laboratory procedures and similar to materials now widely used in advanced electronic interconnect structures. The microstructure was characterized by X-ray diffraction, electron backscattered diffraction, imaging in a field emission scanning electron microscope (FESEM), and microtensile testing. Initial observations indicated microstructural dimensions and mechanical properties in the expected ranges. However, using high-magnification, high resolution imaging in the FESEM, we found a surprising result: the morphology of this electrodeposit resembled an agglomeration of round balls or spheres approximately 30–50 nm in diameter. Both X-ray and electron diffraction results showed grain and subgrain sizes much larger than the individual spheres. Molecular dynamics (MD) simulations of spheres of copper atoms were carried out to interpret the observations, and produced a degree of interpenetration of the spheres that was consistent with the observations. However, in MD simulations of two initially misoriented spheres of up to a thousand atoms, with diameters up to 3 nm and for durations up to 30 ps, the spheres readily agglomerated but remained misoriented. So, the mechanism and rate of crystallographic grain growth within the agglomeration of spheroids remains unknown. This unusual spheroidal morphology may be related to the unusual room-temperature grain growth observed in electrodeposited copper.

Investigation of the effect of chain rigidity on orientation of polymer blends: the case of poly(vinyl phenol)/poly(ethylene terephthalate) blends

Orientation of amorphous, miscible poly(vinyl phenol) (PVPh)-poly(ethylene terephthalate) (PET) blends is studied using experimental and modelling techniques. Up to 50 wt% PVPh, the blends are semi-crystalline and were therefore not studied. At 60 wt% PVPh, no crystallisation was observed using either differential scanning calorimetry or X-ray diffraction. For the 60wt% PVPh blend, FTIR dichroism determination showed that orientation was relatively high (0.09 at a λ=3.4) and similar for both polymers. Above 60 wt% PVPh, however, no appreciable orientation was detected. In order to gain insights about the deformation phenomena in polymer blends, atomistic models of the 60 wt% PVPh composition were built using the Meirovitch approach. These were found in good agreement with X-ray diffraction, and exhibit a fair degree of interpenetration as estimated visually and by comparing intermolecular pair distribution functions. Significant hydrogen bonding was found: 8% of carbonyl oxygens and 1% of carboxylate oxygens of PET are bound to PVPh. Deformation simulations were performed using the Parrinello–Rahman deformation scheme. Orientation of PVPh and PET in the blend was found equivalent to that observed in pure polymers simulations. PET orientation followed the aggregate model and was more oriented than PVPh by a factor of two. It was concluded that the similarity in orientation of the two polymers in the blend, which was observed experimentally on quenched samples, could be due to a combination of different deformation-induced orientation followed by distinct relaxation mechanism and relaxation times for both polymers.

Fine-Tuning the Wetting Behavior of Polyelectrolyte Films with Sodium Dodecyl Sulfate

Charge-alternating polyelectrolyte multilayers containing the anionic surfactant sodium dodecyl sulfate (SDS) were constructed by adsorption from aqueous solution. The polyelectrolyte films contained the polycation PEI (poly(ethylenimine)) and the polyanion PAZO (poly[1-[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl, sodium salt]). SDS adsorption on the PEI/PAZO/PEI trilayer was studied using dynamic tensiometry and single wavelength ellipsometry. Advancing contact angle measurements of SDS adsorption onto PEI surfaces indicate that surfactant adsorption is complete within 1 min. The contact angle increases with surfactant concentration, from 30° (0 mM SDS) and plateaus to a constant value of 80° beyond 0.01 mM SDS. Constructing films from varying concentrations of PEI allowed the degree of PAZO interpenetration to be qualitatively measured. Contact angle and ellipsometric thickness studies indicate that PAZO interpenetrates 32 Å into the terminal PEI layer, above which the surface is composed entirely of PEI. Maximum SDS adsorption is observed above the interpenetrated region, consistent with maximum electrostatic interaction between the terminal PEI layer and SDS.

Static and dynamic mechanical properties of modified bismaleimide and cyanate ester interpenetrating polymer networks

AbstractInterpenetrating polymer networks (IPNs) based on different ratios of modified bismaleimide (BMI) resin [BMI/2,2′‐diallylbisphenol A (DBA)] and cyanate ester (CE) (b10) have been synthesized via prepolymerization followed by thermal curing. A systematic study of both static and dynamic mechanical properties of the cured BMI/DBA–CE IPN resin systems was conducted through flexural, impact testing, and dynamic mechanical analysis (DMA). The static mechanical investigation shows that the flexural strength, flexural strain at break, and impact strength of the cured BMI/DBA–CE IPN resin systems are relatively lower than that calculated by rule of mixture of two individuals: BMI/DBA and b10. However, the flexural moduli of the IPN resin systems have more consistent features compared to that calculated by rule of mixture. Single damping peaks are detected for the cured BMI/DBA–CE IPN resin systems, which suggests a substantial degree of interpenetration between two networks. The damping peaks of the cured BMI/DBA–CE IPN resin systems do tend to become broader with increasing concentration of BMI/DBA, whereas the intensity of damping peaks of the IPN resin systems decreases. The obtained results not only provide insight information about the characteristic structures of these BMI/DBA‐–CE IPN resin systems, but also give guidelines for their applications. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2000–2006, 2003

Chiral direction and interconnection of helical three-connected networks in metal-organic frameworks.

The control of the interpenetration and chirality of a family of metal-organic frameworks is discussed. These systems contain two- (A) and four-fold (B) interpenetration of helical three-connected networks generated by binding the 1,3,5-benzenetricarboxylate (btc) ligand to a metal center. These frameworks have the general formula Ni(3)(btc)(2)X(m)Y(n).solvent (where X = pyridine or 4-picoline, Y = ethylene glycol, 1,2-propanediol, 1,4-butanediol, meso-2,3-butanediol, 1,2,6-hexanetriol, glycerol). The structural and chemical effects of modifying the alcohol and aromatic amine ligands bound to the metal center include controlling the thermal stability and the degree of interpenetration. Covalent linking of the four interpenetrating networks in the A family and the switching of diol binding from mono- to bidentate are demonstrated. Recognition of chiral diols by the hand of the network helices is investigated by binding an alcohol ligand with two chiral centers of opposite sense to the same helix. This reveals the subtle nature of the helix-ligand interaction.

Linear Viscoelastic Properties of Concentrated Solutions of Multi-Arm Star Polystyrenes

The dynamic viscoelasticity of solutions of multi-arm star polystyrenes is investigated. The relaxation spectrum is calculated from the master curves of the dynamic storage and loss moduli. The relaxation spectra for the solutions as well as the melts exhibit a shoulder at long times. The relaxation intensity and the relaxation time for the long time relaxation are estimated from the relaxation spectra. The relaxation intensity strongly depends on the number density of the star molecules, suggesting that the number density dependence of the relaxation intensity is closely related with the degree of interpenetration between the star polymers, while the relaxation time of the long time relaxation is almost independent of the number density of the star molecules.

Three Novel Interpenetrating Diamondoid Networks from Self-Assembly of 1,12-Dodecanedinitrile with Silver(I) Salts

The self-assembly of 1,12-dodecanedinitrile (ddn) with various silver salts (NO3−, PF6−, AsF6−, ClO4−) afforded new polymeric coordination networks with the general formula [Ag(ddn)2]X. All these species contain interpenetrating diamondoid nets showing interesting features: with X=NO3− the cationic [Ag(ddn)2]+ network exhibits the highest interpenetration (tenfold) ever found within diamondoid nets exclusively based on coordinative bonds. When X=PF6− or AsF6− an eightfold diamondoid network is obtained that shows an unusual [4+4] mode of interpenetration, instead of the “normal” set of eight nets equally translated along a principal axis of the adamantanoid cages. The polymeric species that forms with X=ClO4− is a fourfold interpenetrating diamondoid network; the lower degree of interpenetration in this case is related to the conformation assumed by the flexible ddn ligands.

Three novel interpenetrating diamondoid networks from self-assembly of 1,12-dodecanedinitrile with silver(I) salts.

The self-assembly of 1,12-dodecanedinitrile (ddn) with various silver salts (NO(3)(-), PF(6)(-), AsF(6)(-), ClO(4)(-)) afforded new polymeric coordination networks with the general formula [Ag(ddn)(2)]X. All these species contain interpenetrating diamondoid nets showing interesting features: with X=NO(3)(-) the cationic [Ag(ddn)(2)](+) network exhibits the highest interpenetration (tenfold) ever found within diamondoid nets exclusively based on coordinative bonds. When X=PF(6)(-) or AsF(6)(-) an eightfold diamondoid network is obtained that shows an unusual [4+4] mode of interpenetration, instead of the "normal" set of eight nets equally translated along a principal axis of the adamantanoid cages. The polymeric species that forms with X=ClO(4)(-) is a fourfold interpenetrating diamondoid network; the lower degree of interpenetration in this case is related to the conformation assumed by the flexible ddn ligands.

Coordination networks from the self-assembly of silver salts and the linear chain dinitriles NC(CH2)nCN (n = 2 to 7): a systematic investigation of the role of counterions and of the increasing length of the spacers

We have systematically investigated the self-assembly of polymeric networks from six different Ag(I) salts and the flexible linear chain dinitriles NC(CH2)nCN (with n ranging from 2 to 7) in order to obtain some basic information useful for the crystal engineering of coordination frames upon variation of the counterions and of the length of the chains in the bidentate ligands. We have reacted the silver salts AgBF4, AgClO4, AgPF6, AgAsF6, AgSbF6 and AgSO3CF3 with all the dinitriles in ethanol, using metal-to-ligand molar ratios from 1∶1 to 1∶2. All of the products have been structurally characterized, showing, for any combination, the formation of polymeric frameworks. With the exception of two derivatives of AgSO3CF3, all of the other species contain cationic networks with [Ag(dinitrile)2]+ stoichiometry that display two distinct topologies, i.e. 3D diamondoid frames or 2D layers of (4,4)-topology. The diamondoid networks exhibit different degrees of interpenetration (4-fold, 5-fold and 6-fold) which are discussed. The (4,4)-layers form different structures, that include single non-interpenetrated sheets, showing varied stacking modes and interdigitation, 3D arrays deriving from inclined interpenetration of the sheets, and 2D systems of 3-fold parallel entangled layers (a quite unusual degree of interpenetration). Some trends are apparent: for instance, the structure type changes when the anion dimensions exceed some limits, and, moreover, the diamondoid topology is found only with dinitriles having an even number of carbon atoms. Other features, such as the correlation between the anionic size and the dimensions of the cages and of the square meshes, as well as the role of the ligand conformations on the degree of interpenetration, are also discussed.

Polyurethane–unsaturated polyester interpenetrating polymer networks: thermal and dynamic mechanical thermal behaviour

A series of simultaneous interpenetrating polymer networks, IPNs, based on a polyurethane and an unsaturated polyester resin is studied. The curing process was followed using differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR). The IPNs were seen to crosslink completely and the kinetics of the curing process were modified greatly, accelerating with respect to the pure homopolymers. The process of styrene–polyester copolymerization varies from an azeotropic copolymerization in the pure polyester state to alternating copolymerization in the IPNs. Miscibility, phase continuity and phase separation are studied by dynamic mechanical thermal analysis (DMTA). In general, the IPNs obtained have a high degree of interpenetration and are semi-miscibles. Intermediate compositions are slightly less miscible than the outer ranges with a transition for the second component being apparent. The empirical loss modulus–composition curves are compared with those predicted by various theoretical models. In general, the IPNs follow the Budiansky model, which predicts a phase inversion at intermediate compositions. Compositions which are rich in a specific component show a continuous phase with the disperse minority component and the intermediate compositions show two co-continuous phases. It is also seen that these curves depend strongly on the temperature at which they are formed. The loss factor reveals strong synergism and the maximum of properties are found in a composition close to 40% in polyester. Comparison of simultaneous IPNs with sequential IPNs showed that the latter show a lesser tendency to phase separation in the systems studied.

Exploring the Molecular Adhesion of Ocular Mucins

Mucins have been ascribed both pro- and anti-adhesive functions. To clarify how both functions can be embodied in the same molecule we studied the interaction of human ocular mucins with mica and with mucins deposited on mica. Adhesion energy and forces of interaction were evaluated as a function of speed of approach, dwell time at maximum extension, and presence of divalent cations in the imaging buffer. Mucins were tethered to an AFM gold-coated tip. Repeated cycles of approach and retract to mica revealed a large number of adhesions in each cycle. Adhesion energy (0.2-48 aJ) and detachment forces (0.1-4 nN) increased with the addition of Ni(II) ions, and with lengthening dwell time. Speed of approach made little difference to the interactions. Most detachments occurred less than 40 nm from the surface. Inter-detachment distances reflected the major periodicities of the mica basal plane. Short distances of interaction, magnitude of detachment forces, and imaging of mucins on SAM all suggest deformable compact mucin aggregates on the AFM tip. Inter-detachment distances suggest a large degree of interpenetration between neighboring molecules. Tip-tethered mucins did not adhere to mucins deposited on mica. This phenomenon is analogous with the nonadherence of the mucin gels on lids and on cornea during blinking.

Anisotropic Ultra-Small-Angle X-ray Scattering in Carbon Black Filled Polymers

Carbon black (CB) filled polymers display mechanical and electrical properties that depend not only on the volume fraction φ of the filler particles but also on their structure and on their distribution. Recently it has been shown that ultra-small-angle X-ray scattering measurements (USAXS) yield information on the arrangement of aggregates in the fluffy or pelletized CB powder and in particular on their mutual interpenetration. In this paper, USAXS measurements using synchrotron radiation and a two-dimensional detector are reported. They reveal anisotropic features in carbon black filled polymers having a length scale around 100 nm. For CB concentrations below the percolation threshold, no anisotropy is observed, even in uniaxially stretched samples. For concentrations above the threshold, however, the results are highly sensitive to the degree of interpenetration of the CB aggregates. The role of aggregate interpenetration (which can occur because the fractal dimension is smaller than 2) in the mechanical behavior of CB−polymer composites is shown. These features are fully consistent with recent models of reinforcement of rubber by fractal aggregates.